Evidence for a role of accessible galactosyl or mannosyl residues of Fc domain in the in vivo clearance of IgG antibody-coated autologous erythrocytes in the rat.
The potential role of accessible galactosyl or mannosyl residues of IgG in the clearance of IgG-coated autologous red blood cells (IgG-RBCs) by the spleen and the liver was investigated in the rat using rabbit anti-rat RBC IgG antibody molecules differing from each other by their capacity to bind in vitro to peanut agglutinin (PNA) and concanavalin A (Con A), i.e., two lectins that specifically bind to beta-galactosyl and alpha-mannosyl residues of Fc domain, respectively. Those IgG molecules [IgG(PNA) or IgG(Con A)] were separated from the starting anti-RBC IgG antibody batch [IgG(total)] by affinity chromatography on lectin columns. Each IgG-RBC preparation was labeled with 99mTc, and was reinjected iv with autologous rat RBCs labeled with 111In to correct for 99mTc present in the blood contained in each organ. The mean specific spleen uptakes per gram of the three IgG-RBC preparations increased according to the level of RBC sensitization but were at least 10 times higher in each instance than the mean specific liver uptake per gram. Consistent with the clearance curves of IgG(PNA)-RBCs, the mean specific splenic uptake per gram of those RBCs was significantly increased as compared to the same parameters determined using either IgG(total)-RBCs or IgG(Con A)-RBCs. In contrast, the mean specific liver uptakes per gram of IgG(PNA)-RBCs, of IgG(Con A)RBCs, or of IgG(total)-RBCs were not significantly different under otherwise identical experimental conditions. The increase in the splenic removal of IgG(PNA)-RBCs was C3 independent. Furthermore, splenic macrophages isolated from rats were able to bind in vitro significantly more IgG(PNA)-RBCs than IgG(total)-RBCs or IgG(Con A)-RBCs. These data therefore support the concept that, in the rat, the kinetic of removal of IgG-RBCs from the bloodstream by the Fc receptors of splenic mononuclear phagocytes may vary according to the nature of accessible carbohydrates located in the Fc domain of IgG antibody molecules coating the erythrocytes.
Malaise
M G
MG
Service of Rheumatology, State University of Liège, Belgium.
Hoyoux
C
C
Franchimont
P
P
Mahieu
P R
PR
D000818:Animals; D004912:Erythrocytes / Q000276:immunology*; D005260:Female; D005690:Galactose / Q000494:pharmacology*; D007074:Immunoglobulin G / Q000378:metabolism*; D008358:Mannose / Q000494:pharmacology*; D010586:Phagocytes / Q000276:immunology / Q000648:ultrastructure; D051381:Rats; D011919:Rats, Inbred Strains; D011961:Receptors, Fc / Q000502:physiology
D007074:Immunoglobulin G; D011961:Receptors, Fc; D008358:Mannose; D005690:Galactose